The present invention is directed to a torque guarantee system and, more particularly, to a torque guarantee system for use in a process requiring repeated torque application. For example, the torque guarantee system of the present invention may be employed in an assembly line process to guarantee that one or more fasteners of a particular component, or assembly of components, is consistently tightened with a preselected amount of torque.
In many industrial and assembly-type operations, it is often critical that particular fasteners be installed with a predetermined amount of torque. The amount of torque used may be based on a number of factors including, for example, the material(s) through which the fastener(s) passes, the role of the fastener, the environment to which the fastened component(s) will be subjected, and the construction of the fastener itself. For example, if a fastener is overtightened, it may cause unnecessary and undesirable fatigue in the fastener, and/or may damage the component(s) through which it passes. Conversely, if the fastener is to secure a component(s) that will be subjected to a load, to vibration, or to other similar conditions, loosening of the fastener and the component(s) may occur if the fastener is not adequately tightened. Such conditions, as well as other conditions of concern, are commonly encountered, for example, in the field of automotive and/or motorcycle manufacturing. As can be appreciated, there are numerous components, particularly those relating to the engine, suspension, steering and other motive systems of such a vehicle, that could cause serious problems or damage if allowed to loosen during vehicle operation. Obviously, there are also a multitude of other situations and areas of art wherein the proper torquing of fasteners is a concern, and it is not intended that the present invention be limited to any particular field of use.
A proper amount of torque is typically applied to a fastener using a torque wrench or similar device. Such devices are generally operated by hand, but such devices may also be driven by an electric, pneumatic, or hydraulic motor. There is typically a means for manually presetting a torque limit on the device prior to use. Once the preset torque limit is reached during use, the device may, for example, emit an audible or visual signal, or otherwise cease to apply further rotational force to the fastener.
In situations wherein it is critical that a fastener(s) be tightened with a predetermined amount of torque, it is often desirable, at least as an added measure of safety, to somehow confirm that each fastener of interest has indeed been so tightened. To satisfy this desire, numerous methods of torque assurance have been tried. These methods may be as simple, for example, as marking each fastener to indicate that it has been installed with the correct amount of torque. These markings often take the form of a paint blotch or dot, wherein different paint colors may be utilized to indicate different torque levels. However, the success of this method depends entirely on the operator that installs the fastener, or an operator who subsequently checks the fastener for proper torque. As is apparent, it is certainly possible for a fastener that has had an improper torque applied thereto to be marked as correct when employing this method of torque confirmation. For example, an operator may accidentally mark a fastener that was not tightened appropriately, or that was not subsequently checked. Alternatively, it is also possible for an operator to simply mark the fastener(s) without ever knowing what amount of torque was applied to the fastener. While it is not suggested that the latter situation occurs with any particular regularity, it does highlight the dependence of this method on the skill, care, and integrity exercised by the person(s) in charge of installing and/or checking the fastener(s).
Devices have also been developed with features that attempt to control or limit torque. For example, fastener tightening tools exist that provide for automatic operation of the tool under certain conditions, such as the depression of a fastener engaging portion thereof. Other known fastener tightening tools have been designed to terminate the tightening operation upon detection of a preselected torque value, such as by disengaging a motor from a driver portion of the device or by automatically shutting off power to a drive motor. Such tools commonly use sensors, clutches or various other detection means to determine when the predetermined torque value has been reached. Yet other torque applying tools are adapted to monitor the pressure of a supply of air connected thereto and to shut off the air flow if the pressure falls below a preset level. In this manner, consistent operation of the tool is said to be achieved. Still other torque applying tools are provided with safety switches that must be engaged along with a primary device initiator, such as a trigger, before the tool will operate. These safety switches are provided to prevent premature activation of the tool to which they are installed.
None of the aforementioned tools, however, is able to guarantee that a particular fastener, or number of fasteners, has actually been installed with a specific amount of torque. While there are known devices whose use allows an operator to select a particular torque to be applied to a fastener thereby, it is ultimately up to the operator to use these devices properly, and to apply the selected device to each fastener that needs to be so installed. Thus, even if a fastener is subsequently indicated by an operator as being properly torqued, there is no non-human guarantee that such is the case. Consequently, especially with respect to fasteners securing critical components, or to fasteners that are subject to loosening due to vibration, loading, thermal cycling or numerous other conditions, a secondary torque inspection process is commonly employed. In such a process, an operator is generally tasked with checking that one or more particular fasteners has actually been tightened with a predetermined amount of torque. Again, however, the possibility for human error is obvious.
Thus, what is needed, and has to Applicant's knowledge been heretofore unavailable, is a system and method for automatically guaranteeing that a fastener, or a plurality of fasteners, are tightened with an acceptable amount of torque. The system and method of the present invention satisfies this need. The system and method of the present invention guarantees that a fastener(s), or even a non-fastener element, is subjected to a predetermined amount of torque (which may also be hereinafter referred to as “torquing” a fastener(s), or that a fastener(s) has been “torqued”). The torque applied to one or a plurality of fasteners (or non-fastener elements) may be controlled and monitored, and different amounts of torque can be applied to different fasteners. The same applies when the system and method of the present invention is used to apply torque to a non-fastener element. For purposes of clarity, however, the remaining discussion of the present invention will be limited to the use thereof with respect to a fastener installation process.
A process employing the system and method of the present invention will commonly require that an operator proceed through a number of particular process steps before a torque applying tool can be used to tighten the fastener(s) of intetrest. A system controller in communication with various sensors and other process monitoring devices is preferably employed to ensure that the fasteners are properly tightened, and that torque is applied appropriately thereto. Preferably, the system and method of the present invention indicates to a user thereof whether the torque application process was completed successfully, such as through the use of a visual and/or audible signal.
In one exemplary embodiment of the present invention, a system is provided to receive a component, or an assembly of components, having one or more fasteners passing therethrough. When a plurality of fasteners are present, it is possible that one or several of the fasteners requires installation with an amount of torque that is less than that used to install the remaining fasteners. It should be realized that any number of fasteners associated with any combination of torque values may be served by the system and method of the present invention. The component(s) is preferably loaded onto/into a work area, which may optionally employ a fixture or other such structure to receive and properly orient the component(s). However, it should be realized that such a fixture is not critical, or even necessary, to use of the present invention. Once the component(s) is properly loaded onto/into the work area, a preparatory (i.e., pre-fastener installation) process step is performed. In this particular embodiment, Loctite® or another suitable thread locking material is applied to the fastener(s) to be installed to the component(s). Other process steps may also be accomplished prior to installation of the fastener(s). Once the preparatory process(es) is completed, the component(s) is preferably clamped or otherwise held firmly in position in anticipation of fastener installation and torquing. Obviously, clamping of the component(s) could also occur prior to initiation of one or more preparatory process steps.
Only when each of the aforementioned steps has been completed is power supplied to a fastener installation tool provided to tighten the fastener(s). The installation tool may be the device used to provide the proper amount of torque to the fastener(s), or may be a separate tool. The fastener installation tool and/or the torque applying tool may be a hand tool, or may be an air or electric powered wrench, for example. In the former case, an air supply associated with the wrench may be isolated therefrom until the aforementioned steps are completed (i.e., until certain predetermined and monitored conditions are met). In the latter case, electric power may be supplied to the wrench only after said steps are completed.
Generally, there are one or more sensors associated with the system of the present invention. Signals from the sensors are received and analyzed by the system controller. The system controller is provided with data regarding a particular job(s) or process, and subsequently acts to ensure that said process is completed successfully. The system controller is also associated with a torque monitor/controller. It is contemplated that the torque monitor/controller may be integrated into the system controller (i.e., torque monitoring/control may be performed by the system controller), or may be a standalone device that is in communication with the system controller. The data provided to the system controller and/or torque monitor/controller may include an identifier for a particular component or plurality of components that are assembled using a fastener(s) of interest. Different identifiers may have different data associated therewith. The data may include the particular process steps that must be performed prior to fastener installation, the number of fasteners that must be installed with a predetermined amount of torque, and the amount of torque to be applied to each fastener (whether the same or different for the various fasteners). The data may, for example, be made available to the system controller and/or torque monitor/controller as a result of an operator inputting a specific program number or name thereto, or may be an automatic result of loading a particular component, or component assembly, into a work area.
As another example of using the system and method of the present invention, a particular job or process involves the monitored and controlled installation of four fasteners to a component assembly, with two fasteners to be installed with a first torque setting, and two fasteners to be installed with a second torque setting that is less than the first torque setting. In this particular example, the component assembly travels along a moving assembly line. Prior to fastener installation, the component assembly must enter a particular work area, and an operator must initiate the process—such as by engaging a cycle start pushbutton(s) or similar device. Thus, the system controller is provided with data that instructs it to await a cycle start signal. Once the cycle start signal is received, the system controller is programmed to supply power to the particular fastener installation tool provided, which in this particular example may be an electrically-powered combination installation/torque applying tool. The torque monitor/controller subsequently expects the four fasteners to be initially tightened, and subsequently subjected to two different, predetermined, torque settings. The torque monitor/controller is also adapted to monitor the amount of torque applied by the combination tool, and to send setting signals to the torque applying tool, which is adapted to receive said signals and to automatically change its torque setting accordingly. This particular example of using the system and method of the present invention also requires the completion of a post-torquing process, such as a crimping process. The system and method of the present invention prevents the post-torquing process from being initiated unless the torquing process was completed successfully, and may also prevent initiation of a subsequent torquing process unless the post-torquing process is completed successfully.
Therefore, as can be understood from the foregoing description, interlocks are provided that direct the process of interest to be performed in a particular manner. Data provided to and from the system controller and/or torque monitor/controller ensures that a torque applying tool automatically tightens a particular fastener with a specific and predetermined amount of torque. For example, in the latter of the particular processes described above, the fasteners that are to be installed with a lesser amount of torque are also of a different size. Thus, when a provided socket or other fastener engaging means is installed to the torque applying tool, the torque applying tool is automatically set by the torque monitor/controller to install the fastener with the proper amount (lesser amount, in this case) of torque. Consequently, the system controller is able to determine whether all the necessary process steps were completed and that they were completed in the correct order and, through the torque monitor/controller, is able to detect the number of fasteners that have been installed and the amount of torque with which each fastener was installed—thereby enabling the system and method of the present invention to accurately determine whether the overall fastener(s) installation process was successful.
Preferably, the system and method of the present invention provides for indication of successful torque application (and, thereby, a successful fastener installation process), such as by a visual and/or audible signal. Preferably, the system and method of the present invention also provides for indication of unsuccessful torque application, and may also provide specific information as to the source of any problems. For example, it may be indicated that one or more fasteners were not tightened, were not tightened with an adequate amount of torque, or were tightened with an excessive amount of torque. In such case, the present invention may provide the operator with sufficient information to permit correction of the problem. The inability to perform a post-torquing process may also serve as an indication that the torquing process was not completed satisfactorily.
It is contemplated that the system and method of the present invention may be used in conjunction with other equipment and processes, such as downstream assembly equipment in a multi-station assembly process. For example, as described above, it can be understood that a signal from the system of the present invention can be used as an interlock in a downstream process. The system controller and/or torque monitor/controller may also be associated with a database that keeps track of the fastener installation operation for quality control and/or quality assurance purposes. Additionally, while the system and method of the present invention has been described above with specific reference to its use in a fastener installation process, it should be realized that the system and method of the present invention can be employed in virtually any process wherein it is necessary to guarantee that a particular torque has been applied to an element.
A better understanding of the system and method of the present invention can be gained by a reading of the following detailed description of certain exemplary embodiments thereof, in conjunction with reference to the particular drawing figures applicable thereto.